Upgrading mercruiser 350 v8 260 hp

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

Your battery may have had something to do with it. I doubt it though unless there was a bad power connection at the tach. Also check the main harness to the motor. Make sure the pins in that connector are clean.

My tach was getting jumpy. Then got to only working sporadically. Finaly after hitting a big wave one day it quit. I pulled it out and had to use a small screwdriver to bend the backside of the trim ring on it. Pulled it apart and found a bad connection. On the board there were 3-4 post comeing through with a small nut that made the connection to the circuit board and one nut had come off and was bouncing around. I tightened them all back up and it's worked great since.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

Check the connection on my tach... Run HOT wire from battery terminal to ignition on the tach (didn't solve problem still jump past 4,000 rpm)

So i knew the Ignition wire was getting good connection.... Then i ran a ground wire from battery (didn't solve problem still jump past 4,000 rpm)... That tells me i have a good ground.

I was then gonna run the - Coil wire up to my Sender on gauge for the final (wire) test but my woman kept complaining and wanted to head home. So Ive learn a valuable lesson here. No matter how much fun you give someone else on the boat, nobody wants to wait around while your running tests.

So the question is, if i finish my test next time i lunch the boat, do you think that it will solve my tach issues with new wire? It cant be that i have a bad coil right? I mean if it was a bad coil i wouldn't get anything from it. It has to be a bad wire or old wire right?

I will run a separate wire and see whats up.

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

If it was a bad coil it would run rough, run for a while then die, or not run. The tach signal comes from the ignition module and the wiring harness just connects there for the tachometer. Now if the tach is good and you know the connections are good I would try a different coil wire then a different coil. The coil may have a crack in the tower and when you get enough current it could jump from the tower to the neg side of the coil. Or you could have a bad wire. Past that I would try a different tach to see if it does the same thing. You can pick a small one up from an autoparts store fairly cheap or borrow one.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

I have a spare tach. Also i think its time for a new coil though because yesterday while trolling 1.5mph to 2mph for about 15-20 minutes my engine died. Had to start it up again. However i have never had the engine die during regular play. Also, my engine IDL is VERY VERY LOW like mentioned. Its running actually right now at about 600 to 575.. I know 700 or 750 is golden but i think it will push my boat to fast in the docking area.

Coil itself looks old. If its like $20 bucks or so in the local auto store i think ill just pick one up.

Another interesting note, I just remembered i already have an aluminum holley intake manifold on my engine. Its not an upgrade from the original i think except that its aluminum and lighter instead of the cast iron. (from chevy 350) I will look for any markings on it and post an update. But the Edelbrock should still make a differnce compared to my holley because the Edelbrock looks taller.

Also, yesterday we invited a couple friends of ours for boating day so it was 4 total of us. 2 females and 2 males total weight = 600 pounds... total max speed on GPS a whoping 32 MPH!!

Weired how i get 30 mph with 4 people and 15mph with 10=12 people. I guess thats normal. Still wondering how fast i would go by myself.

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

I really don't think you're doing bad in that big of a boat. Get the coil thing taken care of and check the tach. Then prop it right and I think it'll be about as good as it gets with that motor.

You're idle isn't that low. I run a decent sized cam in my 355 and I have my idle set at 600rpm. I'd leave the idle where its at and get the carb dialed in at idle.